Cancer is the second leading cause of death in the United States. To date, approximately 50% of all neoplasms are treated with multi-disciplinary cancer treatment. Neoplastic disorders differ widely in etiology, pathology, and natural disease history. The principle behind detection at earlier stages of disease progression yielding higher cure rates applies to virtually all solid tumors. As a result, cancer screening has been an area of elevated research and clinical interest and has greatly impacted cancer diagnoses and treatments.
Biomarkers are compounds in the body that may be indicative of medical conditions or biological states. Hayes et al. defined a cancer biomarker as “a molecular, cellular, tissue, or process-based alteration that provides indication of current, or more importantly, future behavior of cancer.” See Hayes D F, Bast R C, Desch C E, et al. Tumor marker utility grading system: a framework to evaluate clinical utility of tumor markers. J. Natl. Cancer Inst. 1996, 88, pp. 1456-66. These biological and physiological indicators could include a broad range of biochemical entities, such as nucleic acids, proteins, sugars, lipids, and small metabolites, as well as whole cells, in either specific tissues or in circulation. Today, circulating cancer cells are becoming a powerful tool in “microscopic” cancer screening. Detection of biomarkers, either individually or as larger sets or patterns, can be accomplished by a wide variety of methods, ranging from biochemical analysis of blood or tissue samples to biomedical imaging.
Normally, patients are hesitant to damage their organs and tissues to give samples during the disease diagnosis process. They may also be reluctant to give blood for diagnostic tests. Therefore, development of a noninvasive diagnostic technique for early cancer screening is very crucial for all populations. Noninvasive diagnosis involves procedures that do not penetrate the body mechanically, nor break the skin or involve penetration through a body cavity. It does not require an incision into the body or the removal of biological tissue. Currently, many researchers are focusing on noninvasive means to diagnose cancer by analyzing cancer biomarkers in urine, which is more easily collected than tissue or blood samples.
Recently, pteridine molecules have become a focal point of cancer screening research. See Rokos K., Rokos H., Frisius H., Huefner M., Pteridines in Cancer and Other Diseases, 1983, pp. 153-7; Noronha J. M., Trehan S., Urinary Excretion of Total Pteridines in Cancer, 1990, pp. 515-8; Murr C., Widner B., Wirleitner B., Fuchs D., Neopterin as a Marker for Immune System Activation, Curr. Drug. Metab. 2002, 3, pp. 175-87; Han F., Huynh B. H., Shi H., Lin B., Ma Y., Pteridine Analysis in Urine by Capillary Electrophoresis Using Laser-Induced Fluorescence Detection, Anal. Chem., 1999, 71, pp. 1265-9; Gibbons S. E., Stayton I., Ma Y., Optimization of Urinary Pteridine Analysis Conditions by CE-LIF for Clinical Use in Early Cancer Detection, Electrophoresis, 2009, 30, pp. 3591-7; Fuchs D., Kramer A., Reibnegger G., et al., Neopterin and Beta 2-Microglobulin as Prognostic Indices in Human Immunodeficiency Virus Type 1 Infection, Infection, 1991, 19 (Suppl. 2), pp. S98-S102. Pteridines are a group of heterocyclic compounds contained in the body and excreted in the urine. Research into the use of pteridines as cancer biomarkers investigated the urinary pteridine levels as potential biomarkers for noninvasive diagnosis of cancer. Pteridines are naturally occurring heterocyclic compounds involved in the biosynthetic pathways of cofactors and vitamins. Research suggests that concentrations of pteridines found in urine differ between cancer patients and non-cancer patients. For example, it has been reported that the neopterin/biopterin ratio differs among cancer patients and non-cancer patients. See Stea, B. et al., Clin. Chim. Acta, 1981, 113, pp. 231-242, which reported that the neopterin/biopterin level for cancer patients was 1.6 times that of normal subjects. Additionally, the amount of pteridine and pattern of expression in the urine may vary with specific neoplasms and clinical stage. Thus, urinary pteridine assays have been studied as a potential cancer screening method
Analysis of pteridines has been performed with several techniques, such as thin layer chromatography (TLC), high performance liquid chromatography (HPLC) combined with UV or fluorescence detection, and conventional capillary electrophoresis with laser induced fluorescence detection (CE-LIF). For example, a method has been reported describing the determination of total oncopterin, neopterin, and biopterin in human urine using solid phase extraction with 6,7-dimethylpterin as internal standard and gradient HPLC with fluorescence detection. See Tomandl et al., Journal of Separation Science, Vol. 26, 8, pp. 674-678, June 2003. However, the detection limit for oncopterin reported in the study is relatively high at about 1.43 mol/L. Moreover, the reported urine preparation time is still long (about 2 hr), since the study utilized full hydrolysis vs. oxidation of the pteridines.
In U.S. Pat. No. 6,576,105 B1 by Yinfa Ma, the inventor also described a detection method for pteridines in urine using the conventional CE-LIF technology. Even though the patented CE-LIF technology has shown promising improvements in feasibility for clinical laboratories, the patented CE-LIF technology has limitation on the accuracy and reproducibility because of the complexity of urine samples.
Therefore, there is a need to provide a new and improved cancer screening method by pteridine urine detection using CE-LIF. There is also a need to provide an improved CE-LIF apparatus for the pteridine urine detection to achieve a non-invasive, sensitive, fast, simple, and cost effective cancer screening tool.